Interactions at the vector-host interface may be the most critical to transmission of many arthropod-transmitted infections. Our studies have demonstrated that through the action of their saliva, black-legged ticks (Ixodes scapularis) manipulate the host immune response in a manner that both assures blood feeding success, and also favors survival and transmission of Lyme disease spirochetes (Borrelia burgdorferi). Moreover, these bacteria receive cues from saliva that regulate protein expression, perhaps enhancing invasiveness or survival in the host. These observation now allow us to hypothesize that an effective prevention strategy for Lyme disease, and perhaps other I. scapularis-transmitted infections, can best be developed by manipulating host immune responses to components of vector saliva or saliva-induce microbial products. In the continuation of this project we will purify, clone and produce recombinant tick salivary components, including: an anti-complement protein (Isac), a kininase, and a noel anti-coagulant, for evaluation in vaccine strategies aimed at interrupting tick feeding and preventing disease transmission. Using HPLC protocols and immunological screening of a tick salivary gland cDNA expression library, it should be possible to obtain large quantities of specific recombinant proteins. This strategy will also allow us to identify additional tick salivary components that play important roles in tick feeding and pathogen transmission. We will also clone and produce tick salivary-induced proteins (Sips) of B. burgdorferi, up-regulated at the tick-host interface, for evaluation as candidate vaccine immunogens. Other experiments will test the hypothesis that host immune factors, especially serum complement proteins, prevents B, burgdorferi infection in some species of ticks and may also be responsible for the inability of certain host to serve as infection reservoirs. Most importantly, using a strategy of immunological blocking of tick salivary effector molecules, we will test the hypothesis that salivary proteins are necessary for successfully pathogen transmission. This work will lead us to develop vaccination strategies that combine tick and bacterial elements for prevention of Lyme disease, and possibly a broader range of pathogens.